Evidences for two scales in hadrons

Abstract

Some unusual features observed in hadronic collisions at high energies can be understood assuming that gluons in hadrons are located within small spots occupying only about 10% of the hadrons' area. Such a conjecture about the presence of two scales in hadrons helps to explain the following: why diffractive gluon radiation is so suppressed; why the triple-Pomeron coupling shows no $t$ dependence; why total hadronic cross sections rise so slowly with energy; why diffraction cones shrink so slowly, and why ${\ensuremath{\alpha}}_{\mathbb{P}}^{\ensuremath{'}}\ensuremath{\ll}{\ensuremath{\alpha}}_{\mathbb{R}}^{\ensuremath{'}}$; why the transition from hard to soft regimes in the structure functions occurs at rather large ${Q}^{2}$; why the observed Cronin effect at collider energies is so weak; why hard reactions sensitive to primordial parton motion (direct photon, Drell-Yan dileptons, heavy flavors, back-to-back dihadrons, seagull effect, etc.) demand such a large transverse momenta of the projectile partons, which is not explained by next-to-leading order calculations; why the onset of nuclear shadowing for gluons is so delayed compared to quarks; and why shadowing is so weak.